1. Field of the Invention
This invention relates generally to the art of loose-leaf ring binders and particularly to paper lifters co-acting with binder rings to manage papers.
2. Prior Art
The prior art generally refers to ring binders, loose-leaf ring binders, rings or split rings, prongs, paper lifters, sheet lifters, paper inserts, punched papers, pre-punched sheet, and the like. It is understood that paper sheets and rings co-act. Thus, the spacing of punched holes and rings is a combination. The "rings" are in effect merely prongs that receive the punched papers or sheets, and may have many shapes. These range from true rings to straight bars or rods, to substantially rectangular prongs, and to paired combinations of rings and bars or other paired combination of shapes. The following usage of "rings" or "split rings" is not restricted to circular shapes, but will include any shapes and labels in general use.
Three rings, or sets of split rings, are the most common number and characteristics of rings in a given loose-leaf binder. This is a set that is generally duplicated in the number of holes in the paper inserts, punched papers, sheet, and paper lifters. However, two, five, and seven rings are common examples.
A typical paper lifter is a generally rectangular plate having apertures adapted to fit onto rings in a loose leaf ring binder. The apertures generally align with a transverse side of the lifter and generally provide a fulcrum for the lifter. This general lifter-binder combination presents a type two lever system.
Prior art portrays several sheet lifters. These lifters have in common a general lack of acceptance by the public; reasons include nonperformance, unwieldy to use, and expensive to produce. We will not repeat general reviews of the prior art found in the references. Specific attention will be directed to the following patents:
1. Lewis R. Beyer: "Sheet Lifter," U.S. Pat. No. 3,366,118, dated Jan. 30, 1968, hereinafter Beyer; PA0 2. R. J. Kenkott: "Sheet Lifting Device for a Loose Leaf Binder," U.S. Pat. No. 2,276,987, dated Mar. 17, 1942, hereinafter Kenkott; and PA0 3. J. B. Stuerke: "Fulcrum for Loose Leaf Binders," U.S. Pat. No. 2,505,694, dated Apr. 25, 1950, hereinafter Stuercke. PA0 4. R. S. Mason: "Loose-Leaf Binder," U.S. Pat. No. 3,306,301, hereinafter Mason. PA0 5. I. Maudal: "Double Aperture Paper Lifter," U.S. Pat. No. 5,503,489, hereinafter Maudal.
The Beyer patent shows a standard ring binder with a protective plate over the ring mechanism. An elongated paper lifter inserts transversely over the rings through a plurality of apertures. An inner curved surface extends over the plate and ends in an uninterrupted edge; the curvature is sufficient to rotate the edge to lie flat against the inner circumference of each ring. The apertures and the edge are pressure points acting against the rings; they span an angular arc that is large enough to create components of force that move the lifter along the rings. Outward-sloping ribs are placed on top of the lifter and extend over and well beyond the apertures; their purpose is to slide binder papers away from the rings to prevent tearing of the papers. Ribs are also placed on the underside of the curved surface to prevent opposite pairs of lifters to interlock.
The Beyer patent places emphasis on obtaining sufficient spacing between the pressure points to move the lifter along the rings. The separation between the inner edge and the apertures is therefore determined while both pressure points are against the rings. When the lifter lies flat (ring binder open), the inner edge does not contact the protected plate but is instead suspended well above the plate. Only after rotating a considerable angle following first motion does the inner edge reach the plate. During this initial motion the lifter pivots about the apertures only; consequently, there is no motion of the lifter apertures along the rings. The apertures therefore catch and tear the papers in the binder. The invention inserts outward-sloping ribs to solve this problem, thus causing additional complexity.
Kencott also shows a standard ring binder with a protective plate and lifter apertures engaged with the rings. The load end curls upward over the plate and then closes upon itself to form a closed rocker with an upper shelf. The end of the shelf has a small semicircular notch that abuts the ring. In operation the lifter leverages on the curved rocker portion and rides up the ring on the notch in the shelf end; the shelf pushes the paper sheets.
The rockers must be large to provide a high enough step to raise the paper sheets sufficiently. Thus the rockers become large enough to abut each other when installed as opposing pairs in the ring binder; yet they may not be large enough to fully raise the paper sheets. However, the suspected deficiency is neatly avoided by claiming beneficial co-action between the opposing lifters.
The Stuercke patent shows improvements upon the Kencott invention. One improvement consists of a raised surface mounted on top of the protected plate. This surface serves as an artificial protective plate and raises the height of the lifter. A second improvement is a guide that engages the closed rocker and limits unwanted movements of the lifter. These improvements expressly confirm the reservations noted above about the Kencott invention; yet solves the problem. The result, however, is a cumbersome addition to a prior device.
The Mason patent is included to show a type one lever system. The system includes a channel fastened to the binder book back. A single flat sheet is hinged to the flange edges; the hinge establishes a fulcrum. Apertures provide room for accommodating the rings of the binder. The apertures are only clearance holes, however, and do not provide an additional fulcrum for the lifter.
The Maudal patent is included as a significant prior art. This patent, however, shows a type two lever system where all lever arms are in line with the rings of the binder. They also feature slots for avoiding load arm entanglements with the rings.